Resin composition containing ultrafine inorganic particle

ABSTRACT

By providing a composition in which refractive index can be controlled, and scratch resistivity and adhesion (especially adhesion to a resin having a thiourethane bond or epithiosulfide bond) are excellent when the composition is coated on a base material such as a resin and then cured, the composition comprises (a) a thio(meth)acrylate compound represented by the general formula (1) and (b) ultrafine inorganic particles:  
                 
         wherein a linking(or connecting) group R represents an aliphatic residue, an aromatic residue, an alicyclic residue or a heterocyclic residue or an aliphatic residue having an oxygen atom, a sulfur atom, an aromatic ring, an aliphatic ring, or a heterocycle in the chain; R m  represents each independently a hydrogen atom or a methyl group; and n is an integer of 1 to 4.

TECHNICAL FIELD

The present invention relates to a resin composition comprisingultrafine inorganic particles, and a coating agent and optical materialcomprising the composition.

BACKGROUND ART

Plastic lenses have rapidly come into wise use as lens materials forexample, pickup lenses used for devices for spectacles, cameras, opticalrecording and reproduction instead of glass lenses in view oflightweight, impact resistance, Tintability(Dyeability) and the like.So, radical-polymerized polymer of diethylene glycol bis(allylcarbonate)(hereinafter, D.A.C.) polycarbonate (PC), polymethyl (meth)acrylate(PMMA) and the like have been used for plastic lenses. These plasticlenses have a drawback in that they might be easily scratched ascompared to glasses. As one of measures to handle such a drawback, therewas mentioned of a method for curing a multifunctional (meth)acrylatewith ultraviolet rays (UV), thus forming a tight and hard layer (hardcoatings or Abrasion-resistant coatings) on the surface of a lens.

On the other hand, in order to reduce the thickness of a lens, resinshaving much higher refractive index have been required instead of resinssuch as D.A.C., PC, PMMA and the like having the refractive index ofaround n_(d)=1.49 to 1.58. There have been proposed a resin (aroundn_(d)=1.60 to 1.67) which was obtained by forming a thiourethane bond bythermo-polymerization of a thiol compound and isocyanate compound inJP97-110956A, and a resin (n_(d)=1.70 or more) which was obtained byforming an epithiosulfide bond by ring opening thermo-polymerization ofa thio epoxy compound in JPO2-194083A.

Accompanied with diversity in plastic lenses, especially high refractiveindex, a demand for hard coatings has been diversified. In addition tocharacteristics requiring sufficient scratch resistivity and adherenceto a lens, recently, it has been strongly required that no interferencefringe was generated between the lens surface and hard coatings(refractive indexes of both materials adjusted).

These characteristics for adjusting the refractive index of a basematerial including an optical material are not only required for hardcoatings of a lens, but strongly required for a wide variety of fieldsranging to surface decoration of resin materials, metal materials,ceramic materials, glass materials and the like or adhesive agents, inview of anti-reflection for displays, surface protection for opticalrecording media aesthetically.

However, it is currently difficult to realize hard coatings that satisfyother requirement characteristics (scratch resistivity, adherence andthe like) and in which the refractive index can be adjusted andespecially higher refractive index can be obtained as well.

In JP96-179123A, there has been described a method of curing acomposition comprising multifunctional acrylate and a kind of ultrafineinorganic oxide particles having high refractive index selected fromantimonous oxide, tin oxide, indium-tin mixed oxide, cerium oxide,titanium oxide with ultraviolet rays.

However, as the refractive index of an aliphatic (meth)acrylate such aspentaerythritol triacrylate described in the document or the like is 1.5or less by nature, in order to obtain high refractive index of more than1.6 and more than 1.7, a lot of ultrafine inorganic oxide particleshaving high refractive index should be contained. As a result, a coatinglayer becomes weakened. Furthermore, when a composition having thesealiphatic (meth)acrylate compounds as main components is used as hardcoatings for lenses, as adherence to a resin having the aforementionedthiourethane bond or epithiosulfide bond is not sufficient, it can notbe used.

Also, a method (sol-gel method) of forming hard coatings bythermal-curing of a silane coupling agent as a main component has beenwidely used, in which scratch resistivity was extremely high withcertainty, and adherence to a resin having a thio urethane bond orepithiosulfide bond was sufficient as well. This method, however, haddrawbacks in that heating conditions such as high temperature and longtime were required for forming hard coatings and storage stability of asolution was usually within 1 month.

As a method to form high refractive index layer (film) on the surface ofa resin or glass, there has been a physical method to form a layer suchas titanium oxide, zirconium oxide and the like using vacuumevaporation, sputtering or the like. However, this method has problemsin productivity in view of film production speed or the like, and allowsa thin layer of about several nms, but it is practically difficult toform a thick layer having about several u ms.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a composition in whichthe refractive index can be controlled according to a base material andhard coatings superior in scratch resistivity and adherence (especiallyadherence to a resin having a thio urethane bond or an epithiosulfidebond) can be simply formed.

In order to solve the aforementioned problems, the present inventorshave repeatedly studied and found that a composition comprising (a) athio(meth)acrylate compound represented by the general formula (1) and(b) ultrafine inorganic particles as essential components was a solutionto the above problems and further found that a coating solutioncomprising the composition was excellent in storage stability, thuseasily forming a transparent coat layer having a thickness of severalnms to several Elms or more on a base material.

Furthermore, they have found, that by further adding (c) a(meth)acrylate compound having a (thio)urethane bond, adherence(especially adherence to a resin having a thiourethane bond orepithiosulfide bond), surface hardness, scratch resistivity were furtherimproved and when (d) a hydroxyl group-containing (meth)acrylatecompound and (e) β-diketone compound were added, they could be usedwithout substantially adding a solvent so effect to the human body orenvironment became smaller and a relatively thick molded product couldbe obtained at the same time, thus completing the present invention.

Namely, the present invention relates to:

-   -   (1) a composition comprising (a) a thio(meth)acrylate compound        represented by the general formula (1) and (b) ultrafine        inorganic particles:    -   wherein a linking(or connecting) group R represents an aliphatic        residue, an aromatic residue, an alicyclic residue or a        heterocyclic residue or an aliphatic residue having an oxygen        atom, a sulfur atom, an aromatic ring, an aliphatic ring, or a        heterocycle in the chain; R_(m) represents each independently a        hydrogen atom or a methyl group; and n is an integer of 1 to 4;    -   (2) The composition according to (1), wherein a linking group R        in the general formula (1) is represented by one of the        following formulae (2) to (6):    -   wherein R₁ represents a hydrogen atom or a methyl group; R₂        represents a hydrogen atom, a methyl group or an ethyl group; X₁        and X₂ represent oxygen atoms or sulfur atoms; i is an integer        of 1 to 5; j is an integer of 0 to 2; k, p, q, x, y and z are 0        or 1 respectively;    -   (3) The composition according to (1) or (2), further        comprising (c) a (meth)acrylate compound having a (thio)urethane        bond;    -   (4) The composition according to any one of (1) to (3), further        comprising (d) one or more hydroxyl group-containing        (meth)acrylate compounds represented by the general formulae (7)        to (10) and (e) a β-diketone compound represented by the general        formula (11):    -   wherein R_(m) represents a hydrogen atom or a methyl group; r        and t are an integer of 1 to 4; u is each independently an        integer of 1 to 4; v is each independently an integer of 1 to 4;        and w is each independently an integer of 0 to 4:    -   wherein R₄ and R₅ represent hydrogen atoms or such ones that one        is a hydrogen atom and another is straight chain or branched C₁        to C₄ alkyl group; R₃ and R₆ represent hydrogen atoms or each        independently a hydrogen atom, a C1 to C4 alkyl group, a        hydroxyl group, an aliphatic residue, an aromatic residue, an        alicyclic residue, a heterocyclic residue, or C₁ to C₆ alkyl        group containing one or more ether groups, ester groups,        thioester groups or ketone groups in the chain structure; or R₃        and R₅ may be combined together to form C₅ to C₁₀ rings which        may be substituted with one or more C₂ to C₄ alkylene groups;    -   (5) The composition according to any one of (1) to (4), wherein        a curing film having a coating layer thickness of 2 μm that the        composition is coated on the surface of a resin plate having a        thiourethane bond or an epithiosulfide bond and then cured with        ultraviolet rays has (1) evaluation score of a cross-hatch,        tape-peeling test (JIS-K5400) of 6 or more; and (2) pencil        scratch test value (JIS-K5400) of 3H or more;    -   (6) a coating composition comprising the composition as        described in any one of (1) to (5); and    -   (7) an optical material comprising the composition as described        in any one of (1) to (5) (there are mentioned usage for optical        recording media, lenses, films, light guide plates, light        scattering sheet, prism sheets, sealing materials, adhesives and        the like)

BEST MODE FOR CARRYING OUT THE INVENTION

A composition for coating of the present invention comprises (a)thio(meth)acrylate compounds and (b) ultrafine inorganic particles, andcan be easily formed into a coat layer in which high refractive indexcan be realized, and adherence and scratch resistivity are excellent.

(a) A thio(meth)acrylate compound used in the present invention isrepresented by the aforementioned general formula (1), or morepreferably, wherein the linking group R is a group represented by anyone of the aforementioned formulae (2) to (6). These thio(meth)acrylatecompounds may be used in combination of one or two or more kindsaccording to the physical properties of a cured product.

A method for producing thio(meth)acrylate compounds is described inJP97-25264A. The compounds can be obtained by reacting a thiol compoundwith β-halo propionic acid halogen compound or α-methyl-β-halopropionicacid halogen compound in the absence of a base and then conducting thedehalogenation reaction. As the thio(meth)acrylate compound, compoundsrepresented by the following formulae (12) to (16) can preferably bementioned as thiol compounds can be more easily purchased:

-   -   wherein R_(m) represents each independently a hydrogen atom or a        methyl group; R₁ represents a hydrogen atom or a methyl group;        R₂ represents a hydrogen atom, a methyl group or an ethyl group;        X₁ and X₂ represent oxygen atoms or sulfur atoms; i is an        integer of 1 to 5; j is an integer of 0 to 2; and k, p, q, x, y        and z represent 0 or 1 respectively.

As examples, there can be mentioned, more specifically,(meth)acryloylthiomethylbenzene, benzylthioethyl thio(meth)acrylate whenn=1; 1,2-bis(meth)acryloylthioethane, 1,3-bis(meth)acryloylthiopropane,1,4-bis(meth)acryloylthiobutane, 1,6-bis(meth)bisacryloylthiohexane,bis-2-(meth)acryloylthioethylether, bis-2-(meth)acryloylthioethylsulfide, bis-2-(meth)acryloylthioethylthiomethane,1,2-bis(meth)acryloylthiobenzene, 1,3-bis(meth)acryloylthiobenzene,1,4-bis(meth)acryloylthiobenzene,1,2-bis(meth)acryloylthiomethylbenzene,1,3-bis(meth)acryloylthiomethylbenzene,1,4-bis(meth)acryloylthiomethylbenzene,1,2-bis(2-(meth)acryloylthioethylthio)methylbenzene,1,3-bis(2-(meth)acryloylthioethylthio)methylbenzene,1,4-bis(2-(meth)acryloylthioethylthio)methylbenzene when n=2;1,2-bis(2-(meth)acryloylthioethylthio)-3-(meth)acryloylthiopropane,1,2,3-tris(2-(meth)acryloylthioethylthio)propane when n=3;bis-(2-(meth)acryloylthioethylthio-3-(meth)acryloylthiopropane) sulfidewhen n=4; and the like.

A thiol compound used in production of a thio(meth)acrylate compoundrepresented by the general formula (1) has an aliphatic residue, anaromatic residue, an alicyclic residue or a heterocyclic residue or analiphatic residue having an oxygen atom, a sulfur atom, an aromaticring, an aliphatic ring, or a heterocycle in the chain, and furthercomprises one or more mercapto groups. Specifically, as monothiolcompounds (mercapto group: 1), there can be mentioned, methylmercaptan,ethylmercaptan, propylmercaptan, butylmercaptan, amylmercaptan,hexylmercaptan, heptylmercaptan, octylmercaptan, nonylmercaptan,cyclobentylmercaptan, cyclohexylmercaptan, furfurylmercaptan,thiophenol, thiocresol, ethylthiophenol, benzylmercaptan,benzylthioethylmercaptan; as polythiol compounds (mercapto group: 2 to4), there can be mentioned 1,2-ethanedithiol, 1,2-propanedithiol,1,3-propanedithiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,2,3-propanetrithiol, 1,1-cyclohexanedithiol, 1,2-cyclohexanedithiol,bicyclo[2,2,1]hepta-exo-cis-2,3-dithiol,1,1-bis(mercaptomethyl)cyclohexane, diethylene glycolbis(2-mercaptoacetate), diethylene glycol bis(3-mercapto propionate),bis(2-mercapto ethyl)ether, ethylene glycol bis(2-mercaptoacetate),ethylene glycol bis(3-mercapto propionate), trimethylolpropanebis(2-mercaptoacetate), trimethylol propane bis(3-mercapto propionate,pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritoltetrakis(3-mercapto propionate), 1,2-dimercapto benzene, 1,3-dimercaptobenzene, 1,4-dimercapto benzene, 1,2-bis(mercaptomethyl)benzene,1,3-bis(mercaptomethyl)benzene, 1,4-bis(mercaptomethyl)benzene,1,2-bis(2-mercaptoethyl)benzene, 1,3-bis(2-mercaptoethyl)benzene,1,4-bis(2-mercaptoethyl)benzene, 1,2-bis(2-mercaptoethyleneoxy)benzene,1,3-bis(2-mercaptoethyleneoxy)benzene,1,4-bis(2-mercaptoethyleneoxy)benzene, 1,2,3-trimercaptobenzene,1,2,4-trimercaptobenzene, 1,3,5-trimercaptobenzene,1,2,3-tris(mercaptomethyl)benzene, 1,2,4-tris(mercaptomethyl)benzene,1,3,5-tris(mercaptomethyl)benzene, 1,2,3-tris(2-mercaptoethyl)benzene,1,2,4-tris(2-mercaptoethyl)benzene, 1,3,5-tris(2-mercaptoethyl)benzene,1,2,3-tris(2-mercaptoethyleneoxy)benzene,1,2,4-tris(2-mercaptoethyleneoxy)benzene,1,3,5-tris(2-mercaptoethyleneoxy)benzene, 1,2,3,4-tetramercaptobenzene,1,2,3,5-tetramercaptobenzene, 1,2,4,5-tetramercaptobenzene,1,2,3,4-tetrakis(mercaptomethyl)benzene,1,2,3,5-tetrakis(mercaptomethyl)benzene,1,2,4,5-tetrakis(mercaptomethyl)benzene,1,2,3,4-tetrakis(2-mercaptoethyl)benzene,1,2,3,5-tetrakis(2-mercaptoethyl)benzene,1,2,4,5-tetrakis(2-mercaptoethyl)benzene,1,2,3,4-tetrakis(2-mercaptoethyleneoxy)benzene,1,2,3,5-tetrakis(2-mercaptoethyleneoxy)benzene,1,2,4,5-tetrakis(2-mercaptoethyleneoxy)benzene, 2,2′-dimercaptobiphenyl,4,4′-thiobis-benzenethiol, 4,4′-dimercaptobiphenyl, 4,4′-dimercaptobibenzyl, 2,5-toluenedithiol, 3,4-toluenedithiol,1,4-naphthalenedithiol, 1,5-naphthalenedithiol, 2,6-naphthalenedithiol,2,7-naphthalenedithiol, 2,4-dimethylbenzene-1,3-dithiol,4,5-dimethylbenzene-1,3-dithiol, 9,10-anthracene dimethanethiol,1,2-bis(2-mercaptoethylthio)benzene,1,3-bis(2-mercaptoethylthio)benzene, 1,4-bis(2-meraptoethylthio)benzene,1,2-bis(2-mercaptoethylthiomethyl)benzene,1,3-bis(2-mercaptoethylthiomethyl)benzene,1,4-bis(2-mercaptoethylthiomethyl)benzene,1,2,3-tris(2-mercaptoethylthio)benzene,1,2,4-tris(2-mercaptoethylthio)benzene,1,3,5-tris(2-mercaptoethylthio)benzene,1,2,3,4-tetrakis(2-mercaptoethylthio)benzene,1,2,3,5-tetrakis(2-mercaptoethylthio)benzene,1,2,4,5-tetrakis(2-mercaptoethylthio)benzene,bis(2-mercaptoehtyl)sulfide, bis(2-mercpatoethylthio)methane,1,2-bis(2-mercaptoethylthio)ethane, 1,3-bis(2-mercaptoethylthio)propane,1,2,3-tris(2-mercaptoethylthio)propane,tetrakis(2-mercaptoethylthiomethyl)methane,1,2-bis(2-mercaptoethylthio)propanethiol, 2,5-dimercapto-1,4-dithian,bis(2-mercpatoethyl)disulfide, 3,4-thiophenedithiol,1,2-bis(2-mercaptoethyl)thio-3-mercaptopropane,bis-(2-meraptoethylthio-3-mercaptopropane)sulfide and the like.

Also, as p-halopropionic acid halogen compound ora-methyl-β-halopropionic acid halogen compound, there can be mentioned,specifically, acyl chlorides such as β-chlolo propionic acid, β-bromopropionic acid, α-methyl-β-chlolo propionic acid, α-methyl-β-chlolopropionic acid and the like; and acyl bromides. However, acyl chloridessuch as β-chlolo propionic acid and α-methyl-β-chlolo propionic acid aremore properly used in view of reactivity and the like.

The refractive index can be controlled by adjusting the amount of athio(meth)acrylate compound in (meth)acrylate compounds contained in acomposition. In the weight of (meth)acrylate compound, athio(meth)acrylate compound is preferably more than 1 weight %, morepreferably more than 5 weight %, and further preferably more than 10weight %.

As (b) ultrafine inorganic particles, metal chalcogen compounds such asmetal oxide, metal sulfides and the like; or metal fluorides arepreferable. Specifically, such particles include titanium oxide,zirconium oxide, indium oxide, zinc oxide, selenium oxide, antimonousoxide, tin oxide, lanthanium oxide, neodymium oxide, silicon dioxide,ammonium oxide, zinc sulfide, antimonous sulfide, neodymium fluoride,lanthanium fluoride, magnesium fluoride, sodium fluoride, calciumfluoride, lithium fluoride and the like. By properly adjusting kinds ofultrafine particles and its mixing amount according to usage, purposesand the refractive index of a coating resin, the refractive index can becontrolled.

Specifically, in order to increase the refractive index, ultrafineinorganic particles having high refractive index are combined. In orderto realize the refractive index of particularly 1.7 or more, therefractive index is preferably 1.8 or more in a wavelength of 546 nm.Specifically, such particles include ultrafine particles containing oneor more components of titanium oxide, zirconium oxide, indium oxide,zinc oxide, selenium oxide, antimonous oxide, tin oxide, lanthaniumoxide, neodymium oxide, zinc sulfide and antimonous sulfide, andpreferably containing one or more components of titanium oxide,zirconium oxide, zinc oxide, antimonous oxide, tin oxide and zinc oxide.

On the contrary, when a composition is used for anti-reflection or anadhesive for junction of optical materials and the refractive index ofthe composition is adjusted to be lowered, ultrafine inorganic particleshaving refractive index of 1.6 or less lower than that of athio(meth)acrylate may be combined, which specifically include silicondioxide, neodymium fluoride, lanthanium fluoride, magnesium fluoride,sodium fluoride, calcium fluoride and the like.

Incidentally, when an object is to secure transparency of a resin thatis subject to coating and the like, the average transparency for acoating layer having a thickness of 2 μm in a wavelength of 400 to 600nm is preferably 80% or more, and more preferably 90% or more.

Ultrafine inorganic particles containing two or more componentsspecifically refer to particles forming a structure (core-shellstructure) coated with one or more kinds of other inorganic substanceson the surface of a kind of ultrafine inorganic particle or a crystalstructure consisting of two or more components.

The particle diameter of ultrafine inorganic particles is preferably 1to 50 nm, more preferably 1 to 20 nm, and further preferably 1 to 10 nm.When the particle diameter is greater than 50 nm, it is difficult toobtain a transparent coat layer due to diffusion by particles. When theparticle diameter is smaller than 1 nm, it is difficult to improve therefractive index.

Also, a method for producing ultrafine inorganic particles can belargely divided into a trituration method and a synthetic method.Furthermore, the synthetic method includes a gas phase method such as aevaporation-condensation method, a gas phase reaction method and thelike, while a liquid phase method includes a colloid method, ahomogeneous precipitation method, a hydrothermal synthetic method, amicro-emulsion method and the like.

A method for producing ultrafine inorganic particles used in the presentinvention is not particularly restricted, but production by thesynthetic method is preferable from the viewpoints of the particlediameter, uniformity of a composition, impurities and the like.

It is preferable that each of ultrafine inorganic particles isdispersion-stabilized in a solvent, water or the like, and then acoating agent is produced. As far as the refractive index is not muchreduced, dispersion-stabilized ones are properly used in a method ofadding silane coupling agents such as γ-glycidoxypropyl trimethoxysilane, (meth)acryloyloxy propyl trimethoxy silane, mercaptopropyltrimethoxy silane and the like; organic acids such as carboxylic acidand the like; and polymers such as polyvinyl pyrrolidone, polyvinylalcohol and the like or a method of chemically bonding (surfacemodification) them on the surface of particles.

The amount of ultrafine inorganic particles used is 1 to 400 weightparts to the total 100 weight parts of (meth)acrylate compoundscontained in a composition, preferably 5 to 300 weight parts, and morepreferably 10 to 200 weight parts.

When the amount of ultrafine particles is small, it is difficult toexpect an increase of the refractive index. On the contrary, if theamount is high(or large), defects occur on the coating layer oradherence to a base material is damaged. Incidentally, ultrafineinorganic particles may be used singly or in combination of 2 or morekinds as well. Also, two or more particles having different shape andparticle diameter but the same components may be combined.

By further adding (c) a (meth)acrylate compound having a (thio) urethanebond to a composition comprising (a) a thio(meth)acrylate compound and(b) ultrafine inorganic particles, adherence to a resin, i.e., adherenceespecially even to a resin having a thiourethane bond or anepithiosulfide bond is improved, and surface hardness and scratchresistivity are improved as well.

(c) A (meth)acrylate compound having a (thio)urethane bond can beobtained by the reaction between diiso(thio)cyanate andhydroxy(meth)acrylate. There can be mentioned, specifically, a urethane(meth)acrylate oligomer and the like which can be obtained by thereaction in combination of each of propane diiso(thio)cyanate,hexamethylene diiso(thio)cyanate, isophorone diiso(thio)cyanate,methylene bis(cyclohexyl iso(thio)cyanate), trimethyl hexamethylenediiso(thio)cyanate, tolylene diiso(thio)cyanate, 4,4-diphenylmethanediiso(thio)cyanate, xylene diiso(thio)cyanate, norbornenediiso(thio)cyanate, methyl norbornene diiso(thio)cyanate asdiiso(thio)cyanate; 2-hydroxyethyl(meth)acrylate, 2-hydroxypropylacrylate, glycidol methacrylate, pentaerythritol tri(meth)acrylate,pentaerythritol tetra(meth)acrylate, ethylene glycol, polyethyleneglycol, polypropylene glycol, polytetramethylene glycol and the like ashydroxy(meth)acrylate.

Among these, in order to enhance the hardness after curing, a functionalgroup is preferably bi- or higher functional group, more preferably tri-or higher functional group. It is particularly preferable ifpentaerythritol tri(meth)acrylate is used for a hydroxy(meth)acrylate.

Incidentally, these (meth)acrylate compounds having a (thio)urethanebond may be used in combination of one or more than two kinds accordingto the physical properties of cured products.

The desirable ratio for each component, i.e., (a) a thio(meth)acrylatecompound, (b) ultrafine inorganic particles and (c) a (meth)acrylatecompound having a (thio)urethane bond in the composition is in thefollowing range in view of the surface hardness, adherence and the like.

-   -   (i) (a):(c) is 1 weight %: 99 weight % to 99 weight %: 1 weight        %, preferably 5 weight %: 95 weight % to 95 weight %: 5 weight        %, and more preferably 10 weight %: 90 weight % to 90 weight %:        10 weight %.    -   (ii) (b)/((a)+(b)+(c)) is more than 1 weight % and less than 90        weight %, preferably more than 5 weight % and less than 80        weight %, and more preferably more than 10 weight % and less        than 70 weight %.

Also, when the amount of ultrafine inorganic particles is small in thecomposition having a thio(meth)acrylate compound or a (meth)acrylatecompound having a (thio)urethane bond, it becomes difficult to controlthe refractive index. When the amount of ultrafine inorganic particlesis high(or large) in the composition, on the contrary, a coating layerbecomes weakened and adhesion becomes insufficient.

Furthermore, when (d) one or more hydroxyl group-containing(meth)acrylate compounds represented by the formulae (7) to (10) and (e)P-diketone compound are further added to a composition comprising (a) athio(meth)acrylate compound and (b) ultrafine inorganic particles, asthey can be used without substantially adding a solvent, effect to thehuman body or environment becomes smaller and a relatively thick moldedproduct can be obtained at the same time.

Ultrafine inorganic particles generally tend to be dispersion-stabilizedin a hydrophilic organic solvent, while the same tendency is detectedwhen ultrafine inorganic particles are dispersed in a hydrophilic(meth)acrylate containing a hydroxyl group. Furthermore, by adding aβ-diketone compound, a thio(meth)acrylate compound and ultrafineinorganic particles show a tendency to be dispersion-stabilized.

As a (d) a hydroxyl group-containing (meth)acrylate compound, there canbe mentioned compounds represented by the formulae (7) to (10).Specifically, the following compounds can be mentioned; 2-hydroxy ethyl(meth)acrylate (═HE (M) A), 3-hydroxy propyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy propyl (meth)acrylate, 2-hydroxy butyl(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxy (meth)acrylate,pentaerythritol tri(meth)acrylate. These compounds may be used singly orin combination of two or more kinds.

The desirable ratio for (a) a thio(meth)acrylate compound, (b) ultrafineinorganic particles and (d) a hydroxyl group-containing (meth)acrylatecompound is in the following range in view of the stability of acomposition.

(iii) (a):(d) is 1 weight %: 99 weight % to 99 weight %: 1 weight %,preferably 5 weight %: 95 weight % to 95 weight %: 5 weight %, and morepreferably 10 weight %: 90 weight % to 90 weight %: 10 weight %.

When the amount of a thio(meth)acrylate compound is small, highrefractive index can not be expected. When the amount of a hydroxylgroup-containing (meth)acrylate compound is extremely small, gooddispersibility cannot be obtained.

(iv) (b)/((a)+(b)+(d)) is more than 1 weight % and less than 90 weight%, preferably more than 5 weight % and less than 80 weight %, and morepreferably more than 10 weight % and less than 70 weight %.

When the amount of ultrafine inorganic particles is small in thecomposition, it becomes difficult to control the refractive index. Whenthe amount of ultrafine inorganic particles is high(or large) in thecomposition, gelation and whiting of the composition, and cohesion andprecipitation of ultrafine inorganic particles might easily occurbecause no solvent is actually added.

As (e) a β-diketone compound, there can be mentioned, specifically,those represented by (11), and more specifically, 2,4-pentanedion(acetyl acetone), 3-methyl-2,4-pentanedion, 3-isopropyl-2,4-pentanedion, 2,2-dimethyl-3,5-hexanedion, 1,3-diphenyl-1,3-propanedion,1,3-cyclopentadion, acetoacetic acid, dimethyl maronate, meton and thelike.

The amount of β-diketone compound used is 0.1 to 100 weight parts to 100weight parts of ultrafine inorganic particles, preferably 1 to 50 weightparts, and more preferably 5 to 30 weight parts. When the amount addedis small, good dispersion can not be obtained. When the amount ishigh(or large), there is a possibility that curability of athio(meth)acrylate might be influenced.

Incidentally, it is more preferable to improve the general physicalproperties as described above (adherence to a resin, surface hardness,scratch resistivity, dispersion stability or the like) by adding (c) to(e) components to (a) and (b) components completely.

Furthermore, in order to adjust the physical properties of a curedproduct, an acrylic oligomer/monomer other than a thioacrylate having 2or more (meth)acryloyloxy groups in a molecule may be combined in anycomposition.

Specifically, there can be mentioned, for example, triethylene glycoldi(meth)acrylate, polyethylene glycol di(meth)acrylate, neo benzylglycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanedioldi(meth)acrylate, dimethylol tricyclodecane di(meth)acrylate,trimethylol propane tri(meth)acrylate, ethylene oxide-modifiedtrimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate,pentaerythritol tetra(meth)acrylate, dipentaerythritolhexa(meth)acrylate, bisphenol A diglycidyl ether (meth)acrylic acidadduct, 1,1,3,3,5,5-hexa((meth)acryloxy) cyclotriphosphozene,1,1,3,3,5,5-hexa(meth)acryloxy ethyloxy) cyclotriphosphozene and thelike.

Also, a (meth)acrylic monomer having a (meth)acryloyloxy group in amolecule may be combined for the purpose of adjustment of the viscosityand the like. Specifically, there can be mentioned isoamyl(meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate,butoxyethyl (meth)acrylate, ethoxy diethylene glycol (meth)acrylate,methoxy triethylene glycol (meth)acrylate, methoxy polyethylene glycol(meth)acrylate, methoxy dipropylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, tetra hydrofurfuryl (meth)acrylate,isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, (meth)acrylicacid, (meth)acrylic acid glycidyl, 2-(meth)acryloyloxyethyl-succinicacid, 2-(meth)acryloyloxyethyl phthalic acid, isooctyl (meth)acrylate,isomyristyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, methyl(meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl(meth)acrylate, cyclohexyl methacrylate, benzyl (meth)acrylate,(meth)acryloyl morpholine and the like.

Also, a reactive monomer having a plurality of vinyl groups or thiolgroups may be added for the purpose of producing the viscosity orcontrolling curability as well.

Specifically, there can be mentioned, for example, N-vinyl pyrrolidone,N-vinyl carbazol, vinyl acetate, trimethylolpropanebis(2-mercaptoacetate), trimethylol propane bis(3-mercapto propionate),pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol (3-mercaptopropionate)and the like.

Also, in order to promote curing with ultraviolet rays or heat, a photoor thermal polymerization initiator may be combined.

As photopolymerization initiators, commercial ones can be used ingeneral. Particularly, there can be mentioned, for example, benzophenon,2,2-dimethoxy-1,2-diphenylethane-1-on (a product of Ciba SpecialtyChemicals Inc.; Irgacure-651), 1-hydroxy-cyclohexyl-phenyl-ketone (aproduct of Ciba Specialty Chemicals Inc.; Irgacure-184),2-hydroxy-2-methyl-1-phenyl-propane-1-on (a product of Ciba SpecialtyChemicals Inc.; Darocure-1173, a product of Lamberti s.p.a.;Esacure-KL200), oligo(2-hydroxy-2-methyl-1-phenyl-propane-1-on) (aproduct of Lamberti s.p.a., Esacure-KIP150),(2-hydroxyethyl)-phenyl)-2-hydroxy-2-methyl-1-propane-1-on) (a productof Ciba Specialty Chemicals Inc.; Irgacure-2959),2-methyl-1(4-(methylthio)phenyl)-2-molphorino propane-1-on (a product ofCiba Specialty Chemicals Inc.; Irgacure-907),2-benzyl-2-dimethylamino-1-(4-molphorino phenyl)-butanone-1 (a productof Ciba Specialty Chemicals Inc.; Irgacure-369),bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (a product of CibaSpecialty Chemicals Inc.; Irgacure-819),bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide (aproduct of Ciba Specialty Chemicals Inc.; CGI403),2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TMDPO, a product ofBASF Corp., Lucirin TPO; a product of Ciba Specialty Chemicals Inc.,Darocure-TPO), thioxanthone or derivatives thereof and the like. One ortwo or more kinds thereof may be used in combination.

Furthermore, tertiary amines, for example, triethanolamine,ethyl-4-dimethylaminobenzoate, isopentyl methylaminobenzoate and thelike may be added according to the purpose of photosensitized action.

As a thermal polymerization initiator, peroxides such as benzoylperoxide (BPO) and the like; azo compounds such asazobisisobutyronitrile (AIBN) and the like are mainly used. The amountof an initiator to be combined is usually around 0.1 to 10 weight partsto 100 weight parts of a composition ((meth)acrylate and ultrafineinorganic particles).

When the amount of a photo (thermal) polymerization initiator to begenerally added is small, good curability can not be obtained. When theamount is excessively high(or large), performance proportionate to theamount can not be obtained, on the contrary, the resolved product mighthave a bad effect such as muddiness upon the physical properties of acured product.

When a solvent is added, as a solvent, there can be mentioned, forexample, water or polar organic solvents, i.e., lower alcohols such asmethyl alcohol, ethyl alcohol, isopropyl alcohol and the like; dimethylformamide, N,N′-dimethyl acetamide, N-methyl-2-pyrrolidone,methylcellosolve, ethylcellosolve, butylcellosolve, ethylene glycol,tetrahydrofuran, dioxane, toluene of a low polar solvent and the like.The viscosity of a coating solution can be adjusted by a coating methodon a base material, but preferably 0.1 to 10000 cp, more preferably 0.5to 500 cp, and further preferably 1 to 100 cp.

In a composition for coating, various additives such as ultraviolet rayabsorbent, anti-oxidant, silicon-series surfactant and the like can becombined according to purposes.

As methods to evaluate adherence of hard coatings and to evaluate itssurface hardness, there can be mentioned a cross-hatch, tape-peelingtest (JIS-K5400) and pencil scratch test value (JIS-K5400) respectively.For a curing layer of 2 μm thickness coated on the surface of a resinplate and cured with ultraviolet rays, (1) evaluation score of across-hatch, tape-peeling test (JIS-K5400) takes preferably more than 6and more preferably more than 8; and (2) pencil scratch test value(JIS-K5400) is preferably more than 3H and more preferably more than 4H.

Also, storage stability (pot life) of a composition is preferably onemonth or more for storage at room temperature and 6 months or more forstorage in a refrigerator (4° C.), and more preferably 6 months or morefor storage at room temperature and a year or more for storage in arefrigerator (4° C.).

[Coat Method, Curing Method and Molding Method]

When the composition is coated on a base material, methods such as dip,spin coat, spray and the like can be adopted.

As a light source necessary for photopolymerization, a variety of lowpressure, high pressure, ultra high pressure mercury lamps, chemicallamps, metal halide lamps and the like can be used. The time to conductphotopolymerization is preferably 1 second to 10 minutes. If it takesless than 1 second, sufficient photocuring cannot be conducted. If ittakes more than 10 minutes, a coating layer and a base material aredeteriorated so coloring, deflection or the like might occur in somecases. In curing process, the composition is coated on a base materialand then a solvent in the composition is dried as needed. Dryingtemperature and time are determined by the boiling point of a solventused.

The temperature condition necessary for thermal polymerization isgenerally 50° C. or more, preferably 80° C. or more. However, it isdetermined by the boiling point of a solvent to be used, thermostabe(orheat-resistant) temperature of a base material and the kind of a thermalpolymerization initiator.

When the volatile component of a substantial solvent or the like is notcontained, the composition is introduced to a mold comprising a glassmold and a gasket for photocuring to obtain a thick plate having severalmms or more.

[Usage of a Composition of the Present Invention]

The composition of the present invention can be widely used as therefractive index can be controlled, and scratch resistivity andadherence are excellent and transparency is extremely high if thecomposition is coated on a base material such as a resin or the like andthen cured. Namely, by coating the composition, the composition can beused as spectacles, camera lenses, pickup lenses of devices for opticalrecording and reproduction, and hard coatings of film lenses. Inaddition to that, it can be used for anti-reflection layer for liquidcrystal display, EL display and CRT display; anti-reflection layer of acolor filter for color separation used for liquid crystal devices;surface protective film for printed matters used to reduce lightreflection from the surface of the printed matter by protecting thesurface of so-called printed matters guiding plate; sign board; posterand the like, and it is further used for anti-reflection layers ofmaterials for windows and doors, light cover or helmet shield.

Furthermore, it can be used as surface protective materials for opticalrecording media, high refractive index film for reading and writing ofhigh density recording optical media; surface ornamentation materialssuch as resin materials, metal materials, ceramic materials, glassmaterials, artificial marble and the like aesthetically; adhesives forjunction of optical materials such as lenses, waveguide and the like aswell.

Also, by using a mold or the like, it can be molded as spectacle lenses,pickup lenses, prism sheet, micro-lens arrays.

EXAMPLES

The present invention is described specifically below by way ofProduction Examples and Examples. However, the present invention is notrestricted to these Production Examples and Examples.

1. Production of Ultrafine Inorganic Particle Dispersion

Production Example 1

[Synthesis of Ultrafine Titanium Oxide Particles and Production ofDispersion]

7.5 ml (corresponding to Ti: 0.036 mol) of titanium oxychloride·HCLaqueous solution (Fluka reagent Hydrochloric acid: 38 to 42%, Ti:approximately 15%) was dissolved in 1000 ml of ion exchange water andstirred at a temperature of 70° C. to obtain an aqueous solution ofbluish titanium oxide colloid after 5 hours.

PH of colloid aqueous solution was adjusted near 5 by ion dialysis, andthen a solvent was converted into methylcellosolve according to theconcentration method. 1.0 g of acrylic acid as a dispersing agent wasfurther added thereto and the resulting solution was sufficientlystirred to obtain a methylcellosolve dispersion of titanium oxide of 20%solid content weight. The thus-obtained sol solution was partiallydropped to mesh and an electronic microscope reagent was prepared. As aresult of observation, a titanium oxide crystal having an averageparticle diameter of 5 nm was confirmed.

Production Example 2

[Synthesis of Ultrafine Zirconium Oxide Particles and Production ofDispersion]

10.5 g of zirconium oxychloride octahydrated salt (a product of WakoPure Chemical Industries, Ltd., corresponding to Zr: 0.036 mol) wasdissolved in 1000 ml of ion exchange water and then stirred at atemperature of 100° C. to obtain an aqueous solution of bluish zirconiumoxide colloid solution after 20 hours. PH of colloid aqueous solutionwas adjusted near 4 by ion dialysis, and then a solvent was convertedinto methylcellosolve according to the concentration method. 1.0 g ofacrylic acid as a dispersing agent was further added thereto and theresulting solution was sufficiently stirred to obtain a methylcellosolvedispersion of zirconium oxide of 20% solid content weight. An averageparticle diameter was 10 nm.

Production Example 3

[Synthesis of Ultrafine Zirconium Oxide-coated Titanium Oxide Particlesand Production of Dispersion]

A bluish titanium oxide colloid solution was obtained according to themethod in Production Example 1.

6.4 g (corresponding to Zr: 0.020 mol) of zirconium oxychlorideoctahydrate was added to the colloid solution and the reaction solutionwas prepared at a temperature of 100° C. and stirred for 5 hours. As aresult, a blue-white sol solution in a slurry form was obtained. PH ofthe colloid aqueous solution was adjusted near 5 by ion dialysis, andthen a solvent was converted into methylcellosolve according to theconcentration method. 1.0 g of acrylic acid as a dispersing agent wasfurther added thereto and the resulting solution was sufficientlystirred to obtain a methylcellosolve dispersion of ultrafine zirconiumoxide-coated titanium oxide particles of 20% solid content weight.

Production Example 4

[Synthesis of Ultrafine Zinc Oxide Particles and Production ofDispersion]

2.6 g (0.066 mol) of sodium hydroxide was dissolved in 720 ml ofethanol. 4.8 g (corresponding to Zn: 0.016 mol) of zinc nitratehexahydrate was further added thereto and the reaction solution wasprepared at a temperature of 70° C. and stirred for 2 hours. Thereaction mixture generated white precipitation for about 2 hours,recovered precipitation by centrifugation and was washed with methanolfive times. Methylcellosolve was added thereto, and then 1.0 g ofpolyvinyl pyrrolidone as a dispersing agent was added; the resultingsolution was sufficiently stirred to obtain a dispersion of 20% solidcontent weight. An average particle diameter was 5 nm.

Production Example 5

[Synthesis of Ultrafine Zinc Sulfide Particles and Production ofDispersion]

3.7 g (0.010 mol) of zinc perchloric acid hexahydrate was dissolved in30 ml of methanol. 2.9 g (0.020 mol) of octanethiol was added theretoand the reaction solution was stirred at room temperature. Thereto,mixed gas in which concentration of hydrogen sulfide to helium (hydrogensulfide/helium) was adjusted to be 5 volume % was introduced for 20minutes under stirring. Furthermore, it took another 20 minutes forstirring without introducing the gas. This procedure was repeated twiceand nitrogen gas was introduced for 10 minutes and stirred at the sametime. As a result, a blue-white colloid solution was obtained. Whenammonium gas was introduced and stirred, white precipitation wasobtained. After precipitation was recovered by centrifugation, theprecipitation was washed with methanol 5 times, and then tetrahydrofuranwas added thereto, and the resulting solution was sufficiently stirredto obtain a dispersion of 20% solid content weight.

Production Example 6

[Production of Ultrafine Tin Oxide Particle Dispersion]

Water in 20.0 g of 10 weight % aqueous solution of tin oxide, a productof Taki Chemical Co., Ltd. (product name: Cerames C-10, a tin oxideparticle diameter of 2 nm) was converted into methylcellosolve accordingto the concentration method. Furthermore, in order to bedispersion-stabilized, 1.0 g of an acrylic acid was added thereto, andthe resulting solution was sufficiently stirred to obtain amethylcellosolve dispersion of 10% solid content weight.

Production Example 7

[Production of Ultrafine Antimonous Oxide Particle Dispersion]

Methanol in methanol dispersion (product name: AMT-130S, a antimonousoxide particle diameter of 10 to 20 nm) of antimonous oxide, a productof Nissan Chemicals, Ltd., was converted into methylcellosolve accordingto the concentration method. Furthermore, in order to bedispersion-stabilized, 1.0 g of an acrylic acid was added thereto, andthe resulting solution was sufficiently stirred to obtain amethylcellosolve dispersion of 20% solid content weight.

Production Example 8

[Production of Ultrafine Aluminium Oxide Particle Dispersion]

Water in 10.0 g of 20 weight % water dispersion (product name:Aluminasol-520, a aluminium oxide particle diameter of 10 nm×20 nm) ofaluminium oxide, a product of Nissan Chemicals, Ltd., was converted intomethylcellosolve according to the concentration method. Furthermore, inorder to be dispersion-stabilized, 1.0 g of an acrylic acid was addedthereto, and the resulting solution was sufficiently stirred to obtain amethylcellosolve dispersion of 20% solid content weight.

Production Example 9

[Production of Ultrafine Silicon Dioxide (Silica) Particle Dispersion]

30 weight % MIBK dispersion (product name: Colloidal Silica SnowtexMIBK-ST, a particle diameter of 10 to 20 nm) of ultrafine silicondioxide particles, a product of Nissan Chemicals, Ltd., were dilutedwith MIBK dispersion of 20% solid content weight to prepare adispersion.

2. Production and Evaluation of a Composition of the Present Invention

Example 1

10.0 g (solid content 2.0 g) (769 weight parts as dispersion) of 20%methylcellosolve dispersion of titanium oxide obtained in ProductionExample 1, 1.04 g (80 weight parts) of bis-2-acryloylthioethyl sulfideand 0.26 g (20 weight parts) of pentaerythritol triacrylatehexamethylene diisocyanate urethane pre-polymer (Kyoeisha Chemical Co.,Ltd., a product name: UA-306H) were mixed, and then 3.0 g (230 weightparts) of ethylcellosolve was added thereto. Furthermore,0.17 g (13weight parts) of 2,4,6-trimethylbenzoyl-diphenyl-phophine oxide (TMDPO)as a photo-initiator and Si-series surfactant (Nippon Unicar Co., Ltd.,product name: FZ-2110) was added thereto, and the resulting solution wassufficiently stirred to produce a composition for coating. Then,evaluation was conducted in a method as described later (100 weightparts of acrylate component and 154 weight parts of ultrafine particlecomponent).

Examples 2 to 15

Each composition in Examples 2 to 15 was produced in the same manner asin Example 1, except that compositions shown in Table 1 ware usedinstead. Then, evaluation was conducted in a method as described later.

Incidentally, the formulae (17) to (22) were used for athio(meth)acrylate.

Comparative Example 1

2.6 g (80 weight parts) of bis-2-acryloylthioethyl sulfide, 0.65 g (20weight parts) of pentaerythritol triacrylate hexamethylene diisocyanateurethane pre-polymer (Kyoeisha Chemical Co., Ltd., a product name:UA-306H) were mixed, and then 10.0 g (308 weight parts) ofethylcellosolve was added thereto. Furthermore, 0.17 g (5.2 weightparts) of 2,4,6-trimethyl benzoyl-diphenyl-phosphine oxide (TMDPO) as aphoto-initiator and Si-series surfactant (a product of Nippon UnicarCo., Ltd., product name: FZ-2110) were added thereto, and the resultingsolution was sufficiently stirred to produce a composition for coating.Then, evaluation was conducted in a method as described later.

Comparative Examples 2 to 7

Each composition in Comparative Examples 2 to 7 was produced in the samemanner as in Comparative Example 1, except that compositions shown inTable 1 ware used instead. Then, evaluation was conducted in a method asdescribed later.

Evaluation of a composition for coating having high refractive index wasconducted as follows.

Each coating solution produced in Examples 1 to 15 and ComparativeExamples 1 to 7 was coated on a quartz board, polycarbonate (PC) board,polymethyl methacrylate (PMMA) board having a thickness of 2 mmrespectively by spin coat, dried at room temperature for an hour andthen thereon was irradiated a metal halide lamp (intensity: 120W/cm) for60 seconds, thus forming a hard coat film having a thickness of 0.5 to 2μm.

Furthermore, a coating solution in Example 10 was spin-coated in thesame manner and dried at room temperature for an hour, heat-treated at50° C. for 10 minutes in a hot air drier and then further heat-treatedat 100° C. for 30 minutes. Incidentally, the results were indicated inTable 1.

(1) Refractive Index:

A coating layer formed on the quartz board was measured by ellipsometry(a product of JASCO Inc., M-150). Also, the difference of the refractiveindex between a product in which ultrafine inorganic particles werecombined and a product in which ultrafine inorganic particles were notcombined was represented by A n.

(2) Scratch Resistivity:

A coating layer and PMMA board (a product of Mitsubishi Rayon) as acomparison were scrubbed with an iron wool numbered 0000 to determinethe degree of scratch of the coating film as compared to the PMMA boardand evaluated in the following three steps.

-   -   ◯ . . . Scratched less than PMMA    -   Δ . . . Scratched equal to PMMA    -   x . . . Scratched greater than PMMA

The results were ◯ (Scratched less than PMMA) in all of the cases.

(3) Light Resistance Test:

A sample coated on the quartz board was irradiated using a solarsimulator for 200 hours.

-   -   ◯ . . . No yellowing    -   Δ . . . Yellowing    -   x . . . Film weakened

The results were a little Δ (Yellowing) in Example 1 and ◯ (Noyellowing) in the rest of the cases.

(4) Adherence Test:

The cross-hatch, tape-peeling test (JIS-K5400) was conducted. On thesurface of a coating layer-attached base material (PC and PMMA) wascalibrated and made cut in with a cutter knife at an interval of 2 mm toform 25 scale cells of 4 mm² using a cutter guide (JIS K5400 Rule).Thereon was strongly attached a cellophane adhesive tape (JIS Z1522Rule) and which was then rapidly pulled for counting scale cellsremained on the coat film(or coating layer).

Evaluation Score

-   -   10: No peel-off    -   8: Peel-off in a defect part: within 5% of the total    -   6: Peel-off in a defect part: within 5% to 15% of the total    -   4: Peel-off in a defect part: within 15% to 35% of the total    -   2: Peel-off in a defect part: within 35% to 65% of the total    -   0: Peel-off in a defect part: more than 65% of the total

The results were 10 (No peel-off) for a base material (PC and PMMA).

(5) Appearance, Transparency:

No crack was visually confirmed for a sample coated on a quartz board inwhich no crack was confirmed and the transparency between 400 nm and 600nm was measured by the uv-vis spectrophotometer (Shimadzu UV2200).

-   -   ◯ . . . Over 90% transparency between 400 nm and 600 nm    -   Δ . . . 80 to 90% transparency between 400 nm and 600 nm    -   x . . . Less than 80% transparency between 400 nm and 600 nm        (6) Storage Stability (Pot Life) of a Hard Coating Composition

Each of products in Examples 1 to 15 and Comparative Examples 1 to 7 wasput into a brown sample bottle for sealing completely, and then keptstill standing at a darkroom for a month at room temperature or for 6months at 4° C. to investigate its change.

-   -   ◯ . . . No gelation of a solution and no change in the viscosity    -   Δ . . . No gelation of a solution, but change in the viscosity    -   x . . . Gelation of a solution

The results were ◯ (No gelation of a solution and no change in theviscosity) both at room temperature and at 4° C. TABLE 1 Example ExampleExample Example Example Example Example Remarks 1 2 3 4 5 6 7Composition (a) thioacrylate-1 *1) 80 80 80 80 80 Componentthioacrylate-2 *2) 80 thioacrylate thioacrylate-3 *3) 80 thioacrylate-4*4) thioacrylate-5 *5) thioacrylate-6 *6) (b) TiO2 (solid Production 769(154) Component content 20%) Example 1 Dispersion ZrO2 (solid Production769 (154) (Solid content 20%) Example 2 content) ZrO2—TiO2 (solidProduction 769 (154) 769 (154) content 20%) Example 3 ZnO (solidProduction 769 (154) content 20%) Example 4 ZnS (solid Productioncontent 20%) Example 5 SnO2 (solid Production 1538 (154) content 10%)Example 6 Sb2O5 (solid Production 769 (154) content 20%) Example 7 Al2O3(solid Production content 20%) Example 8 SiO2 (solid Production content20%) Example 9 Acrylate UT-1 *6) 20 20 20 20 20 20 20 HEA *7) DPEHA *8)Initiator TMDPO 13 13 13 13 13 13 13 Darocure-1173 Benzoyl Peroxide(BPO) Solvent Ethylcellosolve 230 230 230 230 230 230 THF MIBK (b) Ratiob/(b + acrylate b: solid 60.6 60.6 60.6 60.6 60.6 60.6 60.6 component)(%) content Total Weight parts 1112 1112 1112 1112 1651 1112 1112Evaluation Results (1) Refractive index 1.78 1.72 1.72 1.71 1.71 1.701.72 Δn(Difference in +0.19 +0.11 +0.13 +0.12 +0.12 +0.11 +0.15particles) (5) Transparency ◯ ◯ ◯ ◯ ◯ ◯ ◯ Example Example ExampleExample Example Example Example Example 8 9 10 11 12 13 14 15Composition (a) thioacrylate-1 80 80 80 80 80 40 Componentthioacrylate-2 thioacrylate thioacrylate-3 thioacrylate-4 80thioacrylate-5 80 thioacrylate-6 40 (b) TiO2 (solid Component content20%) Dispersion ZrO2 (solid (Solid content 20%) content) ZrO2—TiO2(solid 769 (154) 769 (154) 769 (154) 769 (154) content 20%) ZnO (solidcontent 20%) ZnS (solid 769 (154) 769 (154) content 20%) SnO2 (solidcontent 10%) Sb2O5 (solid content 20%) Al2O3 (solid 769 (154) content20%) SiO2 (solid 769 (154) content 20%) Acrylate UT-1 20 20 20 20 20 20HEA 20 10 DPEHA 10 Initiator TMDPO 13 13 13 13 6.5 13 13 Darocure-11736.5 Benzoyl 13 Peroxide (BPO) Solvent Ethylcellosolve 230 230 THF 230230 MIBK 230 (b) Ratio b/(b + acrylate 60.6 60.6 60.6 60.6 60.6 60.660.6 0 component) (%) Total Weight parts 1112 1112 1112 1112 1112 882882 882 Evaluation Results (1) Refractive index 1.71 1.71 1.72 1.61 1.581.72 1.72 1.72 Δn(Difference in +0.11 +0.11 +0.13 +0.02 −0.02 +0.15+0.15 — particles) (5) Transparency ◯ ◯ ◯ Δ ◯ ◯ ◯ ◯ ComparativeComparative Comparative Comparative Comparative Comparative ComparativeExample Example Example Example Example Example Example 1 2 3 4 5 6 7Composition (a) thioacrylate-1 80 80 40 Component thioacrylate-2 80thioacrylate thioacrylate-3 80 thioacrylate-4 80 thioacrylate-5 80thioacrylate-6 40 (b) TiO2 (solid Component content 20%) Dispersion ZrO2(solid (Solid content 20%) content) ZrO2—TiO2 (solid content 20%) ZnO(solid content 20%) ZnS (solid content 20%) SnO2 (solid content 10%)Sb2O5 (solid content 20%) Al2O3 (solid content 20%) SiO2 (solid content20%) Acrylate UT-1 20 20 20 20 20 HEA 20 10 DPEHA 10 Initiator TMDPO 5.25.2 5.2 5.2 5.2 5.2 5.2 Darocure-1173 Benzoyl Peroxide (BPO) SolventEthylcellosolve 308 308 308 308 308 THF MIBK (b) Ratio b/(b + acrylate 00 0 0 0 0 0 component) (%) Total Weight parts 413.5 413.2 413.2 413.2413.2 105.2 105.2 Evaluation Results (1) Refractive index 1.59 1.61 1.571.60 1.6 1.59 1.59 Δn(Difference in — — — — — — — particles) (5)Transparency ◯ ◯ ◯ ◯ ◯ ◯*1) bis-2-acryloylthioethyl sulfide*2) 1,4-bisacryloylthio benzene*3) 1,2-bisacryloylthio ethane*4) 1,2-bis(2-acryloylthioethylthio)-3-acryloyithio propane*5) bis-(2-acryloylthioethylthio-3-acryloylthio propyl) sulfide*6) UT-1: pentaerythritol triacrylate-hexamethylene diisocyanateurethane pre-polymer (a product of Kyoeisha Chemical Co., Ltd.)*7) HEA: 2-hydroxyethyl acrylate*8) DPEHA: dipentaerythritol hexaacrylate3. Production and Evaluation of hard Coating compositions containing aComposition of the Present Invention

Production Example 10

[Production of a Resin Having a Thio Urethane Bond (1)]

36.4 g of m-xylilene diisocyanate represented by the formula (23), 33.6g of 1,2-bis(2-mercaptoethyl)thio-3-mercapto propane represented by theformula (24), 0.01 g of dibutyltin dichloride, and 0.07 g of Zelec UN(STEPAN Co.) as an internal mold release agent were added and stirredfor degassing under reduced pressure for an hour. The resulting mixturewas filtered using 1 μm Teflon (registered trademark) filter and thenwas introduced to a mold comprising a glass mold and a gasket.Temperature of the mold was slowly increased from 40° C. to 120° C.,while polymerizing the mixture for 20 hours. When polymerization wasfinished, the mold was slowly cooled and a resin was taken out of themold. The thus-obtained resin was anneal-treated at 120° C. for 3 hoursto obtain a resin plate (thickness of 5 mm).

Production Example 11

[Production of a Resin Having a Thio Urethane Bond (2)]

37.6 g of m-xylilene diisocyanate, 33.6 g of isomer mixture representedby the formulae (25) to (27), 0.01 g of dibutyltin dichloride, and 0.07g of Zelec UN (STEPAN Co.) as an internal mold release agent were addedand stirred for degassing under reduced pressure for an hour. Theresulting mixture was filtered using 1 μm Teflon (registered trademark)filter and then was introduced to a mold comprising a glass mold and agasket. Temperature of the mold was slowly increased from 40° C. to 120°C., while polymerizing the mixture for 20 hours. When polymerization wasfinished, the mold was slowly cooled and a resin was taken out of themold. The thus-obtained resin was anneal-treated at 120° C. for 3 hoursto obtain a resin plate (thickness of 5 mm).(25)1(26)1(27)=80/10/10 (mol ratio)

Production Example 12

[Production of a Resin having a Thio Urethane bond (3)]

37.6 g of m-xylilene diisocyanate, 27.6 g of bis-2-mercaptoethyl etherrepresented by the formula (28), 0.01 g of dibutyltin dichloride, and0.07 g of Zelec UN (STEPAN Co.) as an internal mold release agent wereadded and stirred for degassing under reduced pressure for an hour. Theresulting mixture was filtered using 1 am Teflon (registered trademark)filter and then was introduced to a mold comprising a glass mold and agasket. Temperature of the mold was slowly increased from 40° C. to 120°C., while polymerizing the mixture for 20 hours. When polymerization wasfinished, the mold was slowly cooled and a resin was taken out of themold. The thus-obtained resin was anneal-treated at 120° C. for 3 hoursto obtain a resin plate (thickness of 5 mm).

Production Example 13

[Production of a Resin having an Epithiosulfide bond (1)]

To 70.0 g of bis(2,3-epithiopropyl) disulfide represented by the formula(29), 0.014 g of N,N-dimethyl cyclohexylamine and 0.07 g ofN,N-dicyclohexylmethylamine were added and stirred for degassing underreduced pressure for an hour. The resulting mixture was filtered using 3μm Teflon (registered trademark) filter and then was introduced to amold comprising a glass mold and a gasket over 4 hours. This mold waskept warm at 30° C. for 10 hours and then temperature of the mold wasincreased from 30° C. to 80° C., while polymerizing the mixture for 20hours. When polymerization was finished, the mold was slowly cooled anda resin was taken out of the mold. The thus-obtained resin wasanneal-treated at 120° C. for 3 hours to obtain a resin plate (thicknessof 5 mm).

Production Example 14

[Production of a Resin having an Epithiosulfide bond (2)]

To 70.0 g of bis(β-epithiopropyl) sulfide represented by the formula(30), 0.35 g of tributylamine was added and stirred for degassing underreduced pressure for an hour. The resulting mixture was filtered using 3μm Teflon (registered trademark) filter and then was introduced to amold over 4 hours. This mold was kept warm at 30° C. for 10 hours andthen temperature of the mold was increased from 30° C. to 120° C., whilepolymerizing the mixture for 20 hours. When polymerization was finished,the mold was slowly cooled and a resin was taken out of the mold. Thethus-obtained resin was anneal-treated at 120° C. for 3 hours to obtaina resin plate (thickness of 5 mm).

Incidentally, in order to remove the internal mold release agentattached to the surface, before conducting evaluation to be describedlater, the resin plate produced in Production Examples 10 to 14 wasdipped in 1 weight % NaOH aqueous solution for 20 minutes, and thensufficiently washed and dried at room temperature.

Example 16

4.0 g (solid content 0.8 g) (171 weight parts as dispersion) of 20% MIBKdispersion of silicon dioxide having a particle diameter of 10 to 20 nmobtained in Production Example 9, 1.17 g (50 weight parts) ofbis-2-acryloylthioethyl sulfide, 1.17 g (50 weight parts) ofpentaerythritol triacrylate isophorone diisocyanate urethane pre-polymer(Kyoeisha Chemical Co., Ltd., a product name: UA-3061) and 0.2 g (9weight parts) of acrylic acid were mixed, and then 3.0 g (128 weightparts) of toluene was added thereto. Furthermore, 0.07 g (3 weightparts) of 2,4,6-trimethylbenzoyl-diphenyl-phophine oxide (TMDPO) as aphoto-initiator was added thereto, and the resulting solution wassufficiently stirred to produce a composition for coating. Then,evaluation was conducted in a method as described later.

Examples 17 to 22

Each composition for Examples 17 to 22 was produced in the same manneras in Example 16, except that compositions shown in Table 2 ware usedinstead. Then, evaluation was conducted in a method as described later.

Comparative Example 8

A coating composition was produced without adding 20% MIBK dispersion ofsilicon dioxide having a particle diameter of 10 to 20 nm in Example 1and then evaluation was conducted in a method as described later.

Comparative Example 9

The same coating composition was produced, except thatbis-2-acryloylthioethyl sulfide in Example 1 was changed tobis-2-acryloyloxyethyl ether (diethylene glycol diacrylate; a reagent ofAldrich Co.) and then evaluation was conducted in a method as describedlater.

Comparative Example 10

The same coating composition was produced, except thatbis-2-acryloylthioethyl sulfide in Example 1 was changed to trimethylolpropane triacrylate (Kyoeisha Chemical Co., Ltd.; a product name: LightAcrylate TMP-A) and then evaluation was conducted in a method asdescribed later.

Evaluation of a hard coating composition was conducted in the followingmanner.

Each of Examples 16 to 22 and Comparative Examples 8 to 10 was coated onthe resin plate in Production Examples 10 to 14 by spin coat, dried at40° C. for a minute in a hot air drier and then thereon was irradiated ametal halide lamp (light intensity: 118 mW/cm² in a wavelength of 365nm) for 20 seconds, thus forming a hard coat film having a thickness of2 μm. Incidentally, the thickness was confirmed according to the surfaceprofiler (DekTakIII, a product of Ulvac, Inc.). Incidentally, theresults of evaluation were indicated in Table 2.

(7) Adherence Test

The cross-hatch, tape-peeling test (JIS K5400) was conducted for afilm-attached sample produced on the resin plates obtained by ProductionExamples 10 to 14 using each of Examples 16 to 22 and ComparativeExamples 8 to 10. On the surface of a coating layer-attached basematerial was calibrated and made cut in with a cutter knife at aninterval of 2 mm to form 25 scale cells of 4 mm² using a cutter guide(JIS K5400 Rule). Thereon was strongly attached a cellophane adhesivetape (JIS Z1522 Rule) and which was then rapidly pulled for countingscale cells remained on the coating layer.

Evaluation Score

-   -   10: No peel-off    -   8: Peel-off in a defect part: within 5% of the total    -   6: Peel-off in a defect part: within 5% to 15% of the total    -   4: Peel-off in a defect part: within 15% to 35% of the total    -   2: Peel-off in a defect part: within 35% to 65% of the total    -   0: Peel-off in a defect part: more than 65% of the total        (8) Pencil Hardness Test

A test based on the handwriting method corresponding to JIS-K5400 wasperformed for a film-attached sample produced on the resin plateobtained by Production Example 10 using each of Examples 16 to 22 andComparative Examples 8 to 10.

Evaluation was conducted by scratches on a coating layer using thepencil of a hardness ranging from 9H to 6B.

(9) Scratch Resistivity Test

A coating layer-attached sample produced on the resin plate obtained byProduction Example 10 using each of Examples 16 to 22 and ComparativeExamples 8 to 10 was loaded with a steel wool (a product of Nippon SteelWool Co., Ltd.) numbered 0000 of 200 g to come and go 10 times forrubbing the surface, and the degree of scratch was visually determinedin the following steps.

-   -   A: No scratch in the range of 1 cm×3 cm    -   B: 1 to 10 scratches in the above range    -   C: 10 to 30 scratches in the above range    -   D: Countless scratches in the above range        (10) Light Resistance Test

A coating layer-attached sample produced on the resin plate obtained byProduction Example 10 using each of Examples 16 to 22 and ComparativeExamples 8 to 10 was irradiated using a solar simulator for 200 hours,and then the peel-off test was conducted for investigation of the statusbefore and after irradiation.

-   -   ◯ . . . No change in adherence    -   Δ . . . Deterioration of adherence slightly    -   x . . . Deterioration of adherence greatly        (11) Appearance, Transparency

In a coating layer-attached sample produced on the resin plate obtainedby Production Example 10 using each of Examples 16 to 22 and ComparativeExamples 8 to 10, appearance was visually measured and thepermeability(or transparency) between 400 nm and 600 nm was measured bythe uv-vis spectrophotometer (Shimadzu UV2200).

-   -   ◯ . . . Over 90% transparency between 400 nm and 600 nm    -   Δ . . . 80 to 90% transparency between 400 nm and 600 nm    -   x . . . Less than 80% transparency between 400 nm and 600 nm

The results were ◯ in all of the cases.

(12) Storage Stability (pot life) of a hard Coating composition

Each of compositions in Example 16 to 22 and Comparative Examples 8 to10 was put into a brown sample bottle for sealing completely, and thenkept still standing at a darkroom for a month at room temperature or for6 months at 4° C., to investigate its change.

-   -   ◯ . . . No gelation of a solution and no change in the viscosity    -   Δ . . . No gelation of a solution, but change in the viscosity    -   x . . . Gelation of a solution

The results were ◯ (No gelation of a solution and no change in theviscosity) both at room temperature and at 4° C. TABLE 2 Example ExampleExample Example Example Remarks 16 17 18 19 20 Composition (a)thioacrylate-1 *1) 50 Component thioacrylate-2 *2) 50 thioacrylatethioacrylate-3 *3) 50 thioacrylate-4 *4) 50 thioacrylate-5 *5) 50Acrylate Acrylic acid 9 9 9 9 9 Dietylene glycol diacrylate TMP-A *9)(b) Component ZrO2 (solid content Production Dispersion 20%) Example 2(solid content) ZrO2—TiO2 (solid content Production 20%) Example 3 SiO2(solid content Production 171 (34) 171 (34) 171 (34) 171 (34) 171 (34)20%) Example 9 (c) UT-1 *6) 50 Component UT-2 *10) 50 50 50 50 Urethaneacrylate Initiator TMDPO 3 3 3 3 3 Solvent Methylcellosolve Toluene 128128 128 128 128 (a):(c) Weight/weight 50:50 50:50 50:50 50:50 50:50 (b)Ratio b/(a + b + c) component (%) b: solid content 25.3 25.3 25.3 25.325.3 Total Weight parts 411 411 411 411 411 Evaluation Results (7)Adherence thiourethane Production 10 10 10 10 10 Test Example 10thiourethane Production 10 10 10 10 10 Example 11 thiourethaneProduction 10 8 10 10 8 Example 12 episulfide Production 10 10 10 10 10Example 13 episulfide Production 10 10 10 10 10 Example 14 (8) PencilHardness Test 5H 5H 5H 5H 4H (9) Scratch Resistivity Test A A A A A (10)Light Resistance Test ◯ ◯ ◯ ◯ ◯ Comparative Example Example ComparativeComparative Example 21 22 Example 8 Example 9 10 Composition (a)thioacrylate-1 50 50 50 Component thioacrylate-2 thioacrylatethioacrylate-3 thioacrylate-4 thioacrylate-5 Acrylate Acrylic acid 9 9 9Dietylene glycol diacrylate 50 TMP-A 50 (b) Component ZrO2 (solidcontent 20%) 171 (34) Dispersion ZrO2—TiO2 (solid content 171 (34)(solid content) 20%) SiO2 (solid content 171 (34) 171 (34) 20%) (c) UT-1Component UT-2 50 50 50 50 50 Urethane acrylate Initiator TMDPO 3 3 3 1313 Solvent Methylcellosolve 128 128 Toluene 128 128 128 (a):(c)Weight/weight 50:50 50:50 50:50 — — (b) Ratio b/(a + b + c) component(%) 25.3 25.3 25.3 0 0 Total Weight parts 411 411 411 411 411 EvaluationResults (7) Adherence thiourethane 8 8 0 10 0 Test thiourethane 8 8 0 100 thiourethane 8 8 0 10 0 episulfide 8 8 0 10 0 episulfide 8 8 0 10 0(8) Pencil Hardness Test 4H 4H 4H H 4H (9) Scratch Resistivity Test B BC D B (10) Light Resistance Test ◯ ◯ — ◯ —*1) bis-2-acryloylthioethyl sulfide*2) 1,4-bisacryloylthio benzene*3) 1,2-bisacryloylthio eta isophorone diisocyanate urethane pre-polymer(a product of Kyoeisha Chemical Co., Ltd.)*4) (1,2-bis(2-acryloylthioethylthio)-3-acryloylthio propane*5) bis-(2-acryloylthioethylthio-3-acryloylthio propyl) sulfide*6) UT-1: pentaerythritol triacrylate-hexamethylene diisocyanateurethane pre-polymer (a product of Kyoeisha Chemical Co., Ltd.*9) TMP-A: trimethylol propane triacrylate (a product of KyoeishaChemical Co., Ltd.)*10) UT-2: pentaerythritol triacrylate4. Production and Evaluation of an Optical Material containing aComposition of the Present Invention

Example 23

A methanol dispersion of 20% solid content weight of ultrafine zirconiumoxide-coated titanium oxide particles as ultrafine inorganic particleswas first obtained in the same manner as in Production Example 3.Furthermore, methanol was changed to 2-hydroxyethyl methacrylate (HEMA)by the concentration method, thus producing 30% solid content weight. Atthis time, the solution tended to be gelated. Acetyl acetone of 20weight % to the ultrafine inorganic particle weight was added andsufficiently stirred. Even when the solution was slowly peptized andeven left at room temperature since then, no gelation was shown. 5.0 g(HEMA: 70 weight parts, ultrafine inorganic particles: 30 weight parts,acetyl acetone: 6 weight parts) of the HEMA ultrafine inorganic particledispersion was taken and 1.65 g (35 weight parts) ofbis-2-acryloylthioethyl sulfide and 0.05 g (1 weight part) of2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TMDPO) as aphoto-initiator were added thereto and sufficiently stirred. Theresulting mixture was filtered using 1 μm Teflon (registered trademark)filter and then introduced to a mold comprising a glass mold and agasket. Thereon was irradiated a metal halide lamp of 120 W/cm type(light intensity: 118 mW/cm² in a wavelength of 365 nm) for 60 seconds.As a result, a transparent resin plate having a thickness of 1 mm wasobtained. An average permeability of the thus-obtained resin plate was82.3%. As a result of measurement using the Abbe refractometer, therefractive index (E line) was 1.69 and Abbe number was 30.

Examples 24 to 28

Each composition as described in Examples 24 to 28 was produced in thesame manner as in Example 23, except that compositions shown in Table 3were used instead, and then evaluation was conducted. TABLE 3 ExampleExample Example Example Example Example Remarks 23 24 25 26 27 28 Com-(a) Component thioacrylate-1 *1) 35 17.5 35 35 35 35 positionthioacrylate-2 *2) 17.5 (b) Component ZrO2—TiO2 Production 30 30 30 3030 (solid content 100%) Example 3 SnO2—ZrO2—Sb2O5 *11) 30 (solid content100%) (d) Component 2-hydroxyethyl 70 70 70 20 30 OH group- methacrylatecontaining 3-hydroxypropyl 70 (meth)acrylate methacrylate2-hydroxy-3-aryloyloxy 50 propyl methacrylate pentaerythritoltriacrylate 40 (e) Component acetyl acetone 6 6 6 6 6 β-diketones3-methyl-2,4-pentadion 6 Initiator TMDPO 1 1 1 1 1 1 (a):(d)Weight/weight 33:67 33:67 33:67 33:67 33:67 33:67 (b) Ratio b/(a + b +d) b: Solid 22 22 22 22 22 22 component (%) content Total Weight parts142 142 142 142 142 142 Evaluation Results Transparency 82.3 81.8 82.280.2 81.8 81.7 Refractive Index (E line) 1.69 1.69 1.69 1.65 1.69 1.68Abbe number 30 28 30 39 28 27*1) bis-2-acryloylthioethyl sulfide*2) 1,4-bisacryloylthio benzene*11): Ultrafine SnO2—ZrO2—Sb2O5 mixed oxide particles (a product ofNissan Chemicals, Ltd., HX-300M1)

INDUSTRIAL APPLICABILITY

A resin composition of the present invention comprises athio(meth)acrylate compound and ultrafine inorganic particles asessential components, enables control of the refractive index asintended by curing with ultraviolet rays, and can be formed into acoating layer superior in scratch resistivity. Thus, it can be used as acoating agent or optical material fields. More specifically, it isuseful for hard coatings of spectacle lens having high refractive index;anti-reflective purposes for plasma display, liquid crystal display, ELdisplay and the like; high refractive index film for reading and writinghigh density recording optical media; optical parts such as opticalfilters and the like; or usages for a surface coating agent and the likeaiming at improving design of plastic materials, metal materials,ceramic materials, glass materials and the like.

In particular, as adherence even to the surface of a resin having a thiourethane bond or epithiosulfide bond and hardness are excellent, thecomposition can be widely applied to hard coat agents of lenses such asspectacle lenses, camera lenses, pickup lenses of devices for opticalrecording and reproduction.

1. A composition comprising (a) a thio(meth)acrylate compound represented by the general formula (1) and (b) ultrafine inorganic particles:

wherein a linking(or connecting) group R represents an aliphatic residue, an aromatic residue, an alicyclic residue or a heterocyclic residue or an aliphatic residue having an oxygen atom, a sulfur atom, an aromatic ring, an aliphatic ring, or a heterocycle in the chain; R_(m) represents each independently a hydrogen atom or a methyl group; and n is an integer of 1 to
 4. 2. The composition according to claim 1, wherein a linking group R in the general formula (1) is represented by one of the following formulae (2) to (6):

wherein R₁ is a hydrogen atom or a methyl group; R₂ represents a hydrogen atom, a methyl group or an ethyl group; X₁ and X₂ represent oxygen atoms or sulfur atoms; i is an integer of 1 to 5; j is an integer of 0 to 2; k, p, q, x, y and z are 0 or 1 respectively.
 3. The composition according to claim 2, further comprising (c) a (meth)acrylate compound having a (thio)urethane bond.
 4. The composition according to claim 3, further comprising (d) one or more hydroxyl group-containing (meth)acrylate compounds represented by the general formulae (7) to (10) and (e) a β-diketone compound represented by the general formula (11):

wherein R_(m) represents a hydrogen atom or a methyl group; r and t are each an integer of 1 to 4; u is each independently an integer of 1 to 4; v is each independently an integer of 1 to 4; w is each independently an integer of 0 to 4:

wherein R₄ and R₅ represent hydrogen atoms or such ones that one is a hydrogen atom and another is a straight chain or branched C, to C₄ alkyl group; R₃ and R₆ represent hydrogen atoms or each independently a hydrogen atom, a C1 to C4 alkyl group, a hydroxyl group, an aliphatic residue, an aromatic residue, an alicyclic residue, a heterocyclic residue, or C₁ to C₆ alkyl group containing one or more ether groups, ester groups, thioester groups or ketone groups in the chain structure; or R₃ and R₅ may be combined together to form C₅ to C₁₀ rings which may be substituted with one or more C₂ to C₄ alkylene groups.
 5. The composition according claim 4, wherein a curing layer of 2 μm thickness that the composition is coated on the surface of a resin plate having a thiourethane bond or an epithiosulfide bond and then cured with ultraviolet rays has (1) evaluation score of a cross-hatch, tape-peeling test (JIS-K5400) of 6 or more; and (2) pencil scratch test value (JIS-K5400) of 3H or more.
 6. A coating composition comprising the composition as described in claim
 5. 7. An optical material comprising the composition as described in claim
 5. 8. The composition according to claim 1, further comprising (c) a (meth)acrylate compound having a (thio)urethane bond.
 9. The composition according to claim 1, further comprising (d) one or more hydroxyl group-containing (meth)acrylate compounds represented by the general formulae (7) to (10) and (e) a β-diketone compound represented by the general formula (11):

wherein R_(m) represents a hydrogen atom or a methyl group; r and t are each an integer of 1 to 4; u is each independently an integer of 1 to 4; v is each independently an integer of 1 to 4; w is each independently an integer of 0 to 4:

wherein R₄ and R₅ represent hydrogen atoms or such ones that one is a hydrogen atom and another is a straight chain or branched C₁ to C₄ alkyl group; R₃ and R₆ represent hydrogen atoms or each independently a hydrogen atom, a C1 to C4 alkyl group, a hydroxyl group, an aliphatic residue, an aromatic residue, an alicyclic residue, a heterocyclic residue, or C₁ to C₆ alkyl group containing one or more ether groups, ester groups, thioester groups or ketone groups in the chain structure; or R₃ and R₅ may be combined together to form C₅ to C₁₀ rings which may be substituted with one or more C₂ to C₄ alkylene groups.
 10. The composition according to claim 1, wherein a curing layer of 2 μm thickness that the composition is coated on the surface of a resin plate having a thiourethane bond or an epithiosulfide bond and then cured with ultraviolet rays has (1) evaluation score of a cross-hatch, tape-peeling test (JIS-K5400) of 6 or more; and (2) pencil scratch test value (JIS-K5400) of 3H or more.
 11. A coating composition comprising the composition as described in claim
 1. 12. An optical material comprising the composition as described in claim
 1. 